For example, one of the very cool demos at Google IO was where you could push a plotted route in Google Maps to your phone. It would be great if, in the background, the phone also loaded all map data along that route and at least saved it to the SD card.
What do you want it to save? The phone doesn't do anything. It just draws information received from Google. Do you want it to store all map tiles at all zoom levels as you drive? Its GPS capability only goes so far as to report a location. If you want an offline navigation system you'll have to use some other system.